Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$167.76	6.783%	$179.1392	$179.14	$179.15	$179.10
Purchase #2	$126.83	3.615%	$131.4149	$131.41	$131.40	$131.40
Purchase #3	$22.31	13.189%	$25.2525	$25.25	$25.25	$25.30
Purchase #4	$223.59	8.665%	$242.9641	$242.96	$242.95	$243.00
Purchase #5	$234.29	13.566%	$266.0738	$266.07	$266.05	$266.10
Purchase #6	$160.98	13.518%	$182.7413	$182.74	$182.75	$182.70
Purchase #7	$107.61	6.443%	$114.5433	$114.54	$114.55	$114.50
7 purchase totals =	$1,043.37		$1,142.1291	$1,142.11	$1,142.10	$1,142.10